This invention relates to a valve assembly for a gas turbine engine. Specifically, this invention relates to a valve assembly that controls the amount of cooling air supplied to a nozzle of a gas turbine engine.
The major components of a typical gas turbine engine may include (beginning at the upstream end, or inlet) a compressor section, a burner (combustor) section, a turbine section, and a nozzle section. The engine may have an afterburner section between the turbine section and the nozzle section.
If the engine is a turbofan, then the compressor section includes a fan section, typically at the upstream end. After passing the fan section, the turbofan engine separates the air into two flow paths. A primary flow (also referred to as core engine flow) enters the remainder of the compressor section, mixes with fuel, and combusts in the burner section. The gases exit the burner section to power the turbine section.
A secondary flow (also referred to as bypass flow) avoids the remainder of the compressor section, the burner section and the turbine section. Instead, the secondary flow travels through a duct to a location downstream of the turbine section. The secondary flow mixes with the primary flow downstream of the turbine section.
The afterburner section may augment the thrust of the engine by igniting additional fuel downstream of the turbine section. The flow then exits the engine through the nozzle.
The engine may supply cooling air to the nozzle in order to protect the nozzle components from the high temperature exhaust. Typically, the engine diverts secondary flow from the fan section to cool the nozzle section.
The greatest demand for cooling air to the nozzle occurs when the afterburner operates. As an example, the pilot operates the engine at maximum thrust (with the afterburner operating) in a conventional take-off and landing (CTOL) operation. CTOL operation typically requires a large amount of cooling air for the nozzle.
Certain non-augmented operations of the engine (i.e., without the afterburner operating) also require cooling air. However, the amount of cooling air need is typically a reduced amount from augmented operations. As an example, a short take-off vertical landing (STOVL) operation typically requires maximum non-augmented thrust from the engine. The non-augmented exhaust, while still at an elevated temperature, typically exhibits a lower temperature than during augmented operations. Accordingly, the engine can accept a reduced supply of cooling air for the nozzle in STOVL operation.
Flow of the cooling air may be controlled by one or more valves. Exemplary valve structures are shown in U.S. Pat. No. 6,694,723, the disclosure of which is incorporated by reference herein as if set forth at length.